If you’re on ubuntu 14.04, you’re mostly on kernel 3.13.x. Maybe even 3.14.x. But, the problem with these is, you can not have a setup like this :
What I mean is, you can not have two monitors connected and all three screens working in harmony, in extended mode. This problem is called a DP MST Problem. DisplayPort Multi-Stream (DP MST) isn’t working, because it does not exist in that kernel version. For the record, I am using a Dell Latitude E7250, and have connected it to a DockStation or Dell E-port, whatever you wanna call it. One external monitor is connected using DVI cable, and other using VGA. You would think this should work, but it doesn’t. Both the external monitors get recognized as just one monitor and they mirror/duplicate each other.
So, to solve this problem, there are two approaches here –
1. Upgrade to ubuntu 15.04 or higher (have out of the box support for DP MST)
2. Upgrade your kernel and intel drivers (I’m assuming you’re having a simple machine having integrated drivers. If you have a graphic card, you MIGHT need to install its drivers too.)
I did not want to update my ubuntu because of LTS version, and knowing that most of my peers are also on 14.04, it was a better choice right now. So, I went ahead with the second method.
On spending some time with the Internet, it told me that Kernel 3.17 added support for DP MST. So, I went ahead and upgraded the kernel.
Here are the commands :
1. Download kernels deb files from here :
Once done, Install in this order :
ii. linux-headers-3.17.4-031704-generic_3.17.4-031704.201411211317_amd64.deb (choose i386 if you have a 32-bit computer)
iii. linux-image-3.17.4-031704-generic_3.17.4-031704.201411211317_amd64.deb (choose i386 if you have a 32-bit computer)
2. Add unofficial xorg repository, so as to get right set of Intel drivers after kernel upgrade.
sudo add-apt-repository:xorg-edgers/ppa sudo apt-get update
3. Once you’re done with this, reboot.
3. You’ll face a “low-graphics mode” session problem. Don’t worry! This is why we have the step 2. You’re doing good till now. Go ahead and say, boot in low-graphics mode for one session. Reboot to boot into low-graphics mode.
But Bhavul, why is this happening?
When you upgrade your kernel, your old graphics driver stay, and those won’t work with newer kernel. One way out is to install unofficial xorg intel drivers, which we do in the next step.
4. Install the unofficial xorg intel driver
sudo apt-get install xserver-xorg-video-intel
5. Reboot. Voila! All 3 screens would work – internal monitor screen and two external displays. 😀
Set up the screens in your own layout using arandr tool or Displays in Settings.
I spent a good amount of time finding a fix for this, and as sad it may sound, tomorrow I have to replace this stunning dell laptop with macbook pro, rendering all the work I did today to get this fixed useless. Unless this post does help you. 🙂